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One-Pot (3 + 2) Cycloaddition-Isomerization-Oxidation of 2,2,2-Trifluorodiazoethane and Styryl Derivatives

Julia Altarejos, Estíbaliz Merino, David Sucunza, Juan J. Vaquero and Javier Carreras*

*Universidad de Alcalá, Departamento de Química Orgánica y Química Inorgánica, 28805, Alcala de Henares, Madrid, Spain, Email: javier.carrerasuah.es

J. Alterejos, E. Merino, D. Sucunza, J. J. Vaquero, J. Carreras, J. Org. Chem., 2023, 88, 11258-11262.

DOI: 10.1021/acs.joc.3c00396


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Abstract

A facile one-pot (3 + 2) cycloaddition-isomerization-oxidation sequence employing 2,2,2-trifluorodiazoethane and styryl derivatives provides 5-aryl-3-trifluoromethylpyrazoles in good yields under mild conditions. The reaction tolerates a broad variety of functional groups.


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Caution

2,2,2-Trifluorodiazoethane should be stored and handled with care due to its toxicity, explosion risk, and low boiling point (gaseous at room temperature).

General procedure for pyrazole synthesis

Trifluorodiazoethane (0.75-1.0 M in DCE, 0.85 mmol) was added to a solution of styrene (5 equiv.), Et3N (2.5 equiv.) and iodobenzene diacetate (1.5 equiv.) in dry DCE (0.75 M, final concentration). The reaction was stirred at 40 °C in a sand bath for 24 hours. The crude was evaporated and purified by column chromatography (hexane/diethyl ether 6:4) to get the corresponding pyrazole.


Key Words

pyrazoles, PIDA


ID: J42-Y2023